Electrolytic manufacture of difficultly-soluble salts of heavy metals.



G. LUCKOW. ELECTROLYTIC MANUFACTURE OF DIFFIOULTLY SOLUBLE SALTS 0F HEA VY'METAL S.

APPLICATION FILED 1111.20, 1910.

1,006,389. i Patented 00b. 17,1911.

(may Lncxow," or concern Germany.

ELECTROLYTIQMANUTACTUBE 013' DIFFICULTLY SOLUIBLE SALTS OF HEAVY METALS.

I I Specification of Letters Patent.

Patented Oct. 17, ,1911.

Application fledianuarv 20, 1910. Serial n 539,206.

all whom it elmcam: Be it known that I, CARL LUGKOW, acitizen of the Empire of Germany, residing at Cologne-on-the-Bhinc, in the Empire of Germany, haveinvented a new and useful Electrolytic Manufacture of Diflicultly-Solu-' ble Salts ofl-leavy Metals, of which the following is a specification.-

Tn my U. S. Patents No. 626,33Lof June 6, 1899, (process of, producing neutral chromate of lead) No. 627,002 ofJ 13, 1899 (proc-' ess of producing White lead by means of .electrolysis) ;.and, No.'62'Z,267 of June 20, 1899 (process of producingbasm phosphateof copper by means of electrolysis) I have described processes of producing insoluble or dificultly soluble salts of heavy metals, the chief feature of which processes consists in that the electrolyte is a very diluted solution of a mixture of a dissolving salt with a preoi itating salt, principally from the class 0 the alkaline metals (inclusive of ammonium), and in that the precipitating salt is constantly regenerated by the continued introduction of fresh acid for replacing that consumed during the process.

My -present invention relates to an electrolytic process for the manufacture of salts of heavy metals which are insoluble or'diflicultly soluble in the electrolyte, in -which manufacture in contradistinction to the above mentioned processes the precipitating salt is completely consumed during the work and therefore requires to be constantly replaced in proportion to the consumption I of its acid'by fresh salt in a suitably diluted til . fill solution. This mode of working renders it necessary to avoid every undesirable percentage or injurious enrichment of the electrolyte with hydroxid of alkali (lye) in the manner,that the latter is always during the work extracted from the electrolyte in a diluted solution by means ofa polar device, as it is produced. This is preferably effected by means of an electrolytic filtration and by removing the polarfiltrate, z'. e. the alkali lye, from the metallic conducting filtering bodies serving as cathodes, which I call fil-' tering cathodes. This new mode of working is suitable, for exam is when the silicic acid by'reason of its di cult solution is replaced by silicates of, alkali (water-glass), and is in all cases preferable, where the V 5 precipitating salts (alkali dichromates,

ali chromates, prussiates of potash, etc.) are theaper than their acids (chromic acid,

ferrocyanic acids etc.), in order to render the manufacture more profitable. In' other cases, where the preclpitating acids are cheaper than their salts, it is of course referable to turn the diluted solutions 0 the hydroxids of alkali running Oflf from the filtering cathodes into diluted solutions of the precipitating salts by the introduction of the respective acids and to always add these salts to the electrolytes as they are consumed. The new manufacture moreover effects a considerable reduction of the consumption of energy or of the voltage requlred, the cathodes being constructed similar to the eleetrodesof storage batteries and serving as depolarizing means.

I willnow roceedto describe. my inven-. tion with re erence to the accompanying drawing, in which- Figure 1 is adiagram ofa-plant foncarrying into efiect the electrolytw. manufacture of white lead, and Fig. 2 is a vertical cross section through the line .AA in Fig. 1'.

Similar characters of reference refer to "similar parts in both views.

In Rigs. 1 and 2 T have for..example illus trated a plantv for carrying into efiect a special mode of the new electrolytic manufacture, viz the process of producing white lead. This plant is shown to comprise only one battery, but it will be understood, that the lant may comprise more than one storageba'ttery with any number of cells each of any known construction. The anodes are denoted by 1 and the cathodesby 2, and all of them are shown to be suspended by means of projections 18 from the upper edges of a suitable vessel 19.

I For carrying the new manufacture into efiect, the following conditions require to be fulfilled:

1:--The anodes v1 are made from the heavy metal or analloy of heavy metals which are to serve as bases ,of the products.

2:The cathodes 2 are substantiallyconstr'ucted similar to the electrodes of storage batteries, for example they are ribbed plates, grates, box-plates etc, the respective metallic plates, being filled or covered with finegrained or finely divided oxids capable of reduction to fun one metals, so that they can serve as depo arizing means for rendering the consumption of energy as economical as possible. The cathodes serving as filters "lyes to' store up in them and to through siphons 6 or the llke.

all of them in one cell or in special cells, are

preferably made in several parts, for ex masses of the filtering cathodes serve not only as depolarizing means but also and more particularly as filters for dividing as far as possible during the work the cathions from the anions, the cathions alone being permitted to enter their interiors 5. Where required, all of the cathodes 2 including the filtering cathodes 3, 4 may be for example inclosed with a wooden frame 20 and filtering cloths 7. p

3 :The electrolyte is a diluted solution of a mixture of two or more salts (either, single or double salts, inorganic or organic salts), more particularly of the alkali metals (1nclusive of ammonium), it being essential, that at least one salt serves as .dissolving salt (that is to say one the anion of which can dissolve the substance of the anodes 1 or form with the latter an easily soluble salt) and at least one salt serves as precipitating salt (that is to say one the anion of which can precipitate the substance of the anodes 1 or form with it a diificultly soluble salt).'

In order to enable the electrolysis to run a regular course, it is necessary that the electrolyte be a very diluted solution and that in the mixture the dissolving salts strongly overweigh the precipitating salts. The reaction of the electrolyte may be weakly acid, neutral or alkaline. The temperature of the electrolyte may be cold, warm or hot.

The substances withdrawn or, separated from the electrolyte during the electrolysis are always or from time to time added as they are consumed. For enabling the oathodes to constantly act as depolarizing means, it is necessary to run off from time to time the electrolyte from the cells (for example through a discharge tube 8, a cock 21 or the like and a trough 16) down to the lower edges of the cathodes 2 and 3, 4 and to allow the fungous metal to which during the work the oxid had been reduced to burn with the oxygen of the air to oxid, which oxidation for examplecan be very well done during the night after every day. During the work the cathions are divided from the anions by electrolytical filtration, the anions although by no means undissolved being prevented or at any rate greatly hindered from penetrating into the filtering bodies serving as cathodes, the filtering bodies permitting only the cathions and the products of the electrolysis to enter them and to store up in them. The polar filtrate of the electrolyte, that is the caustic lye, is then permitted to gradually run off from the filtering cathodes 3, 4

a siphon 3 or the like), as-may be the exceeding diluted solutions of caustic lye running off from the filtering cathodes may be turned into diluted solutions of preclpitating salts by the introduction of the respective acids, whereby the loss of the electrolyte in precipitating salt is compensated, as will be explained later on.

and consequently precipitating.

4: The density of the current is preferabl'y about from 25 to amperes per square meter of the "surface of the anodes, and the tension of the current is about from 1 to 3 volts per cell.

Following three examples will explain the new manufacture:

a. Production of neutral chromate of lead (chrome-yellow).The anodes 1 consist. of soft lead. The cathodes 2 are ribbed plates of soft lead or hard lead with active fillings of lead oxid (fungous lead) preferably all of the cathodes 2 including the filtering cathodes 3, 4 are inclosed with wooden frames 20 and filtering-cloths 7. The electrolyte is a diluted solution containing about one and a half per cent. of a mixture -of about ninety five weight parts of chlorate of sodium and about five weight parts of dichromate of sodium calculated free from water. During the electrolysis dichromate the electrolyte, as they are consumed, and

at the same time the soda-lye is run off from the filtering cathodes; any loss of chlorate of sodium is replaced.

b. Production of Prussian blue and Paris blue.The anodes 1 consist of iron; the cathodes 2 are skeletons of iron with active fillings of iron oxid (fungous iron). The electrolyte is a diluted solution containing about one per cent. of a mixture of about ninety five weight parts of chlorid of potassium or sodium (kitchen-salt) and about five weight parts of ferrocyanid of potassium calculated free from water. During the electrolysis ferrocyanid of potassium or sodium and water are always added to the electrolyte as they are consumed, while the potash or soda-lye is extracted from the filtering cathodes, and any loss of chlorid of potassium or sodium is replaced.

0. Production of basic carbonate of lead (white lead), see Figs. 1 and 2.The anodes 1 consist of soft lead. The cathodes 2 are suitable skeletons of soft lead or hard lead with active fillings of lead oxid (fungous lead); preferably all the cathodes 2 including the filtering cathodes 3, 4 are inclosed with wooden frames 20 and filtering-cloths 7 The electrolyte is a diluted solution containing aboutfrom one to two per cent. of a mixture of about from ninety to ninety five weight parts of chlorate of sodium and about from five to ten weight parts of carbonate of sodium (soda) calculated free from water. Duringtheelectrolysis the soda-lye is always extracted, as it is produced, from the filtering cathodes 4: b means of a siphon 6 or the like and passe through a suitable receptacle 10 for carbonic acid introduced from some source through a tube 11, so that it is thereby turned into a solution of soda, which is conducted through a tube 12 into somereservoir 13 of any known construction. From the reservoir 13 the soda solution is sucked by means of some suitable pump 14 through the suction pipe 15 and is delivered through a tube 9 into the cell or cells in order to be added to the electrolyte.

17 denotes inclined plates for facilitating the collection of the product.

Of course the plant may be varied in various manners obvious to the expert.

I claim:

1. The herein described electrolytic manufacture of salts of heavy metals which are insoluble or difiicultly soluble in the electrolyte, consisting in using anodes of a heavy metal, and cathodes ofa similar metal with depolarizing fillings, a number of the cathodes forming boxes and serving as filtering cathodes, in connection with an aqueous solution as electrolyte containing a small percentage of a mixture of dissolving salt and a precipitating salt, both chiefly from the class of alkali metals (in: elusive of ammonium), and in passing a current through said solution, the precipitating salt being always added, as its acid is consumed, and the hydroxid of alkali developed from the electrolyte and entering the filtering cathodes belng therefrom extracted.

2. The herein described electrolytic manufacture of salts of heavy metals which are insoluble or difficultly soluble in the electrolyte, consisting in using anodes of a heavy metal, and cathodes of a similar metal with depolarizing fillings, a number of the cathodes forming boxes and serving as filtering cathodes, all of the cathodes including the filtering cathodes being inclosed with wooden frames and filtering-cloths, in connection with an aqueous solution as electrolyte containing a small percentage of a mixture of a dissolving salt and a precipitating salt both chiefly from the class of alkali metals (inclusive of ammonium),and in passing a current through said solution, the precipitating salt being always added, as its acid is consumed, and the hydroxid of alkali developed from the electrolyte and entering the filtering cathodes being therefrom extracted.

3. The herein described electrolytic manufacture of basic carbonate of lead (white lead), consisting in using anodes of soft lead, and cathodes of lead with depolarizing fillings of lead oxid, a number of the cathodes forming boxes for serving as filtering cathodes, in connection with an aqueous solution as electrolyte containing about from one to two per cent. of an alkali chlorate in mixture with an alkali carbonate, and in passing a current through said solution, the alkali carbonate and water being always added to the electrolyte as they are consumed, and the lye developed from the electrolyte and entering the filtering cathodes being therefrom extracted.

4:. The herein described electrolytic manufacture of basic carbonate of lead (white lead), consisting in using anodes of soft lead, and cathodes of lead with depolarizing fillings of lead oxid, a number of the cathodes forming boxes for serving as filtering cathodes and all the cathodes including the filtering cathodes being preferably inclosedwith wooden frames and filteringcloths, in connection with an aqueous solution as electrolyte oontainin about from one to two per cent. of an alkali chlorate in mixture with an alkali carbonate, and in passing a current through said solution, the alkali carbonate and water being always added to' the electrolyte as they are consumed, and the lye developed from the electrolyte and entering the filtering cathodes being therefrom extracted.

CARL LUCKOW.

Witnesses LOUIS VANDORY,

BESSIE F. DUNLAP. 

